In discharging particulate material from hoppers, it is not uncommon for the particulate material to form relatively stable formations such as arch formations, domes, bridges and rat holes, which act to prevent the efficient discharge of the particulate material from the hopper. Various methods have been heretofore proposed for breaking up the formations. In copending U.S. application Ser. No. 404,544 filed Aug. 2, 1982, to Pole, commonly assigned herewith, the hopper openings are controlled by one or more gates which are swingable about pivot points to move within the hopper outside of the boundary of the hopper opening controlled by the gate, whereby they can dig into and break up the formations. Generally speaking this necessitates the gates being suspended from within the hopper, which may itself promote the formations spoken of to some extent. Also, it will be appreciated that in certain instances, such as where the particulate material is coal or rock, the particles may be of a relatively large size, whereby gate supporting structure which locates within the hopper may be subject to undue stress and damage.
Where the gate is required to open by movement into the hopper, there is a considerable resistance to such movement until such time as the particulate material commences to be discharged through the gate, and the energy requirements to open the gate in the initial stages are therefor high. As a corollary, the equipment required to generate and transmit the opening forces must be relatively massive, thereby leading to increased costs and size.
It is desirable that the load on the gate act at all times in a manner to urge the gate to a closed position whereby the gate will tend to close in the event of a power failure. On the other hand, there is advantage in a gate system which will remain partially open without necessitating the continuous application of power to maintain it in its open position. Where the particulate material acts to urge the gate to open, it is desirable that means for locking the gate be provided.
It is a prime object of this invention to provide improved apparatus for handling particulate material.
It is another object of the invention to provide hoppers and gate structure therefor.
It is a further object of the invention to provide apparatus of the aforesaid nature wherein the gate supporting structure may locate predominately outside of the hopper.
It is yet another object of the invention to provide gate structure which may assume a stable, partially open position.
It is still a further object of the invention to provide gate structure which may be locked shut.